MARCHANTIA POLYMORPHA. 79 



the root-hairs are not merely rhizoids but real roots, 

 and such they have been called by Sachs recently, who 

 no longer holds to the morphological distinctions of 

 root, stem, leaf and hairs, but refers all vegetative 

 organs of higher plants to two categories, viz : the root 

 and the shoot 



The scales are organs that we shall meet with in a 

 more developed form when we reach the ferns. They 

 differ from the leaves in size and position, but more 

 especially in having the cells empty and lifeless. 



The internal structure of the stem is interesting on 

 account of the thickenings of the cell-walls for secur- 

 ing extra strength, and the absence of any differentia- 

 tion of the tissues along the midrib except the moder- 

 ate change in the shape of the cells. 



The branching of the stem is a fine example of true 

 dichotomy where the growing point is symmetrically 

 halved, and each half gives rise to a branch. 18 In this 

 case one branch develops faster than the other, and 

 the appearance is soon the same as if it had arisen as a 

 lateral branch (see fig. 2). The tissues of the wings 

 reach their growth more rapidly than those of the 

 midrib, and so the growing end is constantly indented. 



The leaves have little of the appearance we associate 

 with the term, as commonly used. They are, indeed, 

 very depauperate leaves, and serve simply as organs 

 of strength, through the power of the protoplasmic 

 contents of the cells to maintain turgidity. 



The asexual propagation in Marchantia is of two 



"Vorlesungen uber Pflanzenphysiclogie, p. 5. 

 'Sachs, Text-book, 2nd Eng. ed., pp. 177, 181. 



